Device and method for mounting electronic parts

ABSTRACT

An electronic components mounting machine comprising an actuator(7), whereby electronic components are mounted on a substrate, a camera(5) whereby coordinates of recognition marks formed on the substrate at four places at least, are detected, a controller(6) whereby actuator(7) is controlled, a mounting data table(9) wherein information on mounting coordinates and mounting angles of electronic components to be mounted is stored, and a correction data table(10) wherein information on correction values to be applied to the mounting coordinates and mounting angles in reference to the substrate, on which the electronic components are mounted, is stored, and characterized in that the correction data table(10) stores information on correction values for each respective cell, which is formed by dividing the substrate into a plurality of small sections according to a specified rule in reference to the coordinates of recognition marks detected by the camera(5), thus enabling to mount each respective electronic component in accordance with the information on the mounting coordinates and mounting angles stored in the mounting data table(9) after the information is corrected according to the information on correction values stored in the correction data table(10) for each respective cell, where a corresponding electronic component is mounted.

FIELD OF THE INVENTION

The present invention relates to an electronic components mountingmachine and a mounting method of electronic components. Especially, thepresent invention is characterized in that electronic components aremounted on a substrate by applying a correction to mounting operationsaccording to deformations of the substrate.

BACKGROUND OF THE INVENTION

In general, almost all the electronic components mounting machines haveso far been provided with capabilities of applying a correction tomounting operations according to deformations observed on a substratewhere electronic components are mounted.

Such a correction applied to prior art electronic components mountingmachines will be explained with reference to FIG. 8.

In FIG. 8(a), recognition marks 2 and 3 are located on each of twocorners of a substrate 1, respectively, where the two corners aresituated diagonally opposite to each other. With a prior art electroniccomponents mounting machine, when the substrate 1 is deformed from anideal configuration as indicated by solid lines in FIG. 8(a) to aconfiguration indicated by dotted lines, the position of the recognitionmark 3 is shifted accordingly. A constant deformation ratio is obtainedby calculation from the magnitude of shifting of the recognition marks 2and 3 and a correction is applied to mounting positions of theelectronic components mounting machine by the use of the deformationratio. In this case, however, it is assumed that the deformation of thesubstrate 1 is taking place uniformly in both the X and Y directions asillustrated in FIG. 8(a).

When deformations appear nonuniformly in the X and Y directions as shownin FIG. 8(b), the two recognition marks 2 and 3 do not provide correctinformation on the deformations, thereby not allowing the deriveddeformation ratio to represent the actual deformations of thesubstrate 1. Particularly, as large size substrates are used more andmore recently, the adverse effect of nonuniform deformations is nolonger neglected.

Thus, the prior art electronic components mounting machines havepresented a problem of inability to cope sufficiently with thedeformations of substrates when large size substrates are used and/or ahigh precision mounting performance is required of electronic componentsmounting machines.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an electronic mountingmachine whereby a high precision mounting performance is achievedthrough a proper process of correction employed against whateverdeformations applied to substrates.

An electronic component mounting machine of the present inventioncomprises an actuator for mounting electronic components on a substrate,a detector for identifying recognition marks that are located at leaston four places of the substrate and detecting coordinates of therecognition marks, a controller to control the foregoing actuator, amounting data table for storing information on mounting coordinates andmounting angles of the electronic components to be mounted and acorrection data table for storing information on correction values to beapplied to the foregoing mounting coordinates and mounting angles inreference to the substrate, on which electronic components are mounted,wherein the foregoing correction data table stores information oncorrection values for each respective cell formed by dividing thesubstrate into a plurality of small sections according to a specifiedrule in reference to the coordinates of at least four recognition marksand the information on the mounting coordinates and angles stored in theforegoing mounting data table is corrected by the information oncorrection values stored in the foregoing correction data tablecorresponding to a cell on the substrate where a specific electroniccomponent is mounted, thereby mounting of the foregoing electroniccomponents being successfully performed.

In the structure as described in the above, a substrate is divided intoa plurality of cells by a specified rule, information on correctionvalues is decided for each respective cell and is stored in a correctiondata table. At this time, these cells are formed according to thecoordinates of recognition marks that are formed on at least four placesof the substrate.

Therefore, when the substrate is deformed nonuniformly in the X and Ydirections that are perpendicular to each other, each respective cellpresents a configuration reflecting the foregoing nonuniformdeformation. Since correction values are obtained for each respectivecell in accordance with these deformations, a correction is made tomatch each respective nonuniform deformation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an electronic components mounting machinein a preferred embodiment of the present invention.

FIG. 2 is another block diagram of an electronic components mountingmachine in a preferred embodiment of the present invention.

FIG. 3(a) is a drawing to describe cells of a master substrate in apreferred embodiment of the present invention.

FIG. 3(b) is a drawing to describe cells of a substrate in a preferredembodiment of the present invention.

FIG. 4 shows the content of a mounting data table in a preferredembodiment of the present invention.

FIG. 5 shows the content of a correction data table in a preferredembodiment of the present invention.

FIG. 6 is a chart to show the relationship between tables in a preferredembodiment of the present invention.

FIG. 7 is a flow chart of an electronic components mounting machine in apreferred embodiment of the present invention.

FIG. 8(a) and FIG. 8(b) describe correction values required of a priorart electronic components mounting machine.

PREFERRED EMBODIMENTS OF THE INVENTION

Next, a preferred embodiment of the present invention will be explainedwith reference to drawings.

FIG. 1 is a block diagram of an electronic components mounting machinein a preferred embodiment of the present invention.

In FIG. 1, a reference numeral 4 indicates a master substrate having nodeformations, reference symbols A, B, C and D indicate recognition markslocated on the four corners of the master substrate 4, respectively, and(xA, yA) is the coordinate of the recognition mark A and similarly (xB,yB), (xC, yC) and (xD, yD) are the coordinates of the recognition marksB, C and D, respectively.

In consideration of a rectangular configuration usually employed with asubstrate, the conditions of xA=xB, xC=xD, yA=yD and yB=yD areestablished.

A reference numeral 5 indicates a video camera for observing the mastersubstrate 4, and each respective coordinate as mentioned in the above isobtained from the video images taken by the video camera 5.

Alternatively, the foregoing coordinates may be decided by the designvalues of the substrate without relying on the master substrate 4.

A reference numeral 6 indicates a controller that controls a driver 8for driving an actuator 7 whereby mounting of electronic components isperformed.

A reference numeral 9 indicates a mounting data table, whereininformation on mounting coordinates and angles relative to electroniccomponents to be mounted is stored, and a reference numeral 10 indicatesa correction data table, wherein correction values for each respectivecell formed by dividing a substrate into small sections vertically andhorizontally are stored.

In FIG. 2, how a substrate 11 to be mounted with electronic components,not the master substrate 4, is observed by means of the video camera 5is illustrated.

The substrate 11 is usually deformed nonuniformly in the X and Ydirections, and accordingly the coordinates (xA', yA'), (xB', yB'),(xC', yC') and (xD', yD') corresponding to recognition marks A', B', C'and D', respctively, and formed on each of the four corners of thesubstrate 11 are deviated from the coordinates of correspondingrecognition marks on the master substrate 4.

Next, the positional relationship and correction values at eachrespctive cell will be explained with reference to FIG. 3.

A system of notation employing subscripts i (i=1, 2, 3, . . . m, m+1)and j (j=1, 2, 3 . . . n, n+1), where m and n are integers, isintroduced here.

Suppose there is a square cell formed by surrounding with line segmentsgi, gi+1, each of which is formed by connecting between a point made bydividing a side AD or side BC of the master substrate 4 equally by m andits neighboring point and line segments fi, fi+1, each of which isformed by connecting between a point made by dividing a side AB or sideDC of the master substrate 4 equally by n and its neighboring point.

Since the square ABCD is rectangular on the master substrate 4, the cellsurrounded by the line segments gi, gi+1 and line segments fi, fi+1 isalso rectangular. Also suppose that a cell R(i, j) with notation ofsubscripts (i, j) has four corner points P(i, j), P(i, j+1), P(i+1, j)and P(i+1, j+1) as shown in FIG. 3.

In addition, the coordinate of the corner point P(i, j) is expressed by(x (i, j), y (i, j)).

When the virtual coordinate of this coordinate system's origin isconsidered as (x (0, 0), y (0, 0)), the equation whereby the coordinateof the corner point P(i, j) is derived from the coordinates of therecognition marks A, B, C and D is generally expressed as follows:##EQU1##

wherein

    (x(0, j), y(0, j))=((xA-xB)j/m+xB, (yA-yB)j/m+yB)

    (x(n, j), y(n, j))=((xD-xC)j/m+xC, (yD-yC)j/m+yC)

    (x(i, 0), y(i, 0))=((xC-xB)j/n+xB, (yC-yB)j/n+yB)

    (x(i, m), y(i, m))=((xD-xA)j/n+xA, (yD-yA)j/n+yA)

and in the case of a rectangle that serves as a basis for the presentexemplary embodiment,

    (x(0, j), y(0, j))=(xB, (yA-yB)j/m+yB)

    (x(n, j), y(n, j))=(xC, (yD-yC)j/m+yC)

    (x(i, 0), y(i, 0))=((xC-xB)j/n+xB, yB)

    (x(i, m), y(i, m))=((xD-xA)j/n+xA, yA)                     (Equation 1)

Also, in connection with a substrate 11, suppose there is a square cellS (i, j) formed by surrounding with line segments g'i, g'i+1, each ofwhich is formed by connecting between a point made by dividing a sideA'D' or side B'C' of the substrate 11 equally by m and its neighboringpoint and line segments fi, fi+1, each of which is formed by connectingbetween a point made by dividing a side A'B' or side D'C' of thesubstrate 11 equally by n and its neighboring point.

The cells S (i, j) are in a one-to-one correspondence with the cells R(i, j).

However, since the square A'B'C'D is not usually rectangular due todeformations of the substrate 11, the cell S (i, j) differs from thecell R (i, j) in not showing a rectangular configuration as shown inFIG. 3(b).

As in the case of the cell R (i, j), suppose the cell S (i, j) has fourcorner points P'(i, j), P'(i+1, j), P'(i, j+1) and P'(i+1, j+1), and thecoordinate of the corner point P'(i, j) is expressed by (x'(i, j), y'(i,j)). The coordinate of the corner point P'(i, j) can also be derivedfrom the coordinates of the recognition marks A', B', C' and D' by usingan equation that is similar to (Equation 1).

In the present exemplary embodiment, the correction value ε in thehorizontal direction is defined as a mean value of shifting values (Δx,Δy) of the four corner points of the cell S (i, j) that correspond tothe four corner points of the cell R (i, j). respectively.

When the correction value of the cell S (i, j) in the X directionagainst the cell R (i, j) is εx(i, j) and the correction value in the Ydirection is a εy(i, j), the correction values εx(i, i) and εy(i, j) canbe obtained from the following equation:

    εx(i, j)=(Δx(i, j)+Δx(i, j+1)+Δx(i+1, j)+Δx(i+1, j+1)/4

    εy(i, j)=(Δy(i, j)+Δy(i, j+1)+Δy(i+1, j)+Δy(i+1, j+1)/4

wherein

    (Δx(i, j), Δy(i, j))=(x'(i, j)-x(i, j), y'(i, j)-y(i, j))

    (Δx(i, j+1), Δy(i, j+1))=(x'(i, j+1)-x(i, j+1), y'(i, j+1)-y(i, j+1))

    (Δx(i+1, j), Δy(i+1, j))=(x'(i+1, j)-x(i+1, j), y'(i+1, j)-y(i+1, j))

    (Δx(i+1, j+1), Δy(i+1, j+1))=(x'(i+1, j+1)-x(i+1, j+1), y'(i+1, j+1)-y(i+1, j+1))                                         (Equation 2)

Further, in the present exemplary embodiment, the rotational correctionvalue ε74 of the cell S (i, j) is defined as a mean value of rotationalshifts a Δθ of the four line segments that correspond to the four linesegments surrounding the cell R (i, j).

In connection with the rotational direction (θ direction), thecorrection value 68 θ (i, j) to be applied to the cell S (i, j) againstthe cell R (i, j) can be obtained from the following equation:

    εθ(i, j)-(Δθfi+Δθfi+1+Δθgi+Δθgi+1)/4

    , wherein f(VA, VB)=ATN(VA, VB)

    (x(0, j), y(0, j))=((xA-xB)j/m+xB, (yA-yB)j/m+yB)

    (x(n, j), y(n, j))=((xD-xC)j/m+xC, (yD-yC)j/m+yC)

    (x(i, 0), y(i, 0))=((xC-xB)i/n+xB, (yC-yB)j/n+yB)

    (x(i, m), y(i, m))=((xD-xA)i/n+xA, (yD-yA)j/n+yA)

and in the case of a rectangle,

    (x(0, j), y(0, j))=(xB, (yA-yB)j/m+yB)

    (x(n, j), y(n, j))=(xC, (yD-yC)j/m+yC)

    (x(i, 0), y(i, 0))=(xC-xB)i/n+xB, yB)

    (x(i, m), y(i, m))=(xD-xA)i/n+xA, yA)

    Δθfi=(VA1, VB1)

    VA1=(y(i, m)-y(i, 0))(x'(i, m))-x'(i, 0))+(y'(i, m)-y'(i, 0))(x(i, m)-x(i, 0))

    VB1=(y(i, m)-y(i, 0))(y'(i, m))-y'(i, 0))+(x(i, m)-x(i, 0))(x'(i, m)-x'(i, 0))

    Δθfi+1=(VA2, VB2)

    VA2=(y(i+1, m)-y(i+1, 0))(x'(i+1, m)-x'(i+1, 0))+(y'(i+1, m)-y'(i+1, 0))(x(i+1, m)-x(i+1, 0))

    VB2=(y(i+1, m)-y(i+1, 0))(y'(i+1, m)-y'(i+1, 0)+(x(i+1, m)-x(i+1, 0))(x'(i+1, m)-x'(i+1, 0))

    Δθgi=(VA3, VB3)

    VA3=(y(n, j)-y(0, j))(x'(n, j)-x'(0, j))+(y'(n, j)-y'(0, j))(x(n, j)-x(0, j))

    VB3=(y(n, j)-y(0, j))(y'(n, j))-y'(0, j))+(x(n, j)-x(0, j))(x'(n, j)-x'(0, j))

    Δθgi+1=(VA4, VB4)

    VA4=(y(n, j+1)-y(0, j+1))(x'(n, j+1)-x'(0, j+1))+(y'(n, j+1)-y'(0, j+1))(x(n, j+1)-x(0, j+1))

    VB4=(y(n, j+1)-y(0, j+1))(y'(n, j+1)-y'(0, j+1))+(x(0, j+1)-x(n, j+1))(x'(n, j+1)-x'(0, j+1))                              (Equation 3)

Thus, by the use of (Equation 1), (Equation 2) and (Equation 3) thecorrection values εx(i, j), εy(i, j) and εθ (i, j) of the fragmentedcell S (i, j) can be obtained from the coordinates of the detectedrecognition marks A', B', C' and D' by calculation.

FIG. 4 shows the contents of a mounting data table in a preferredembodiment of the present invention, and FIG. 5 shows the contents of acorrection data table in the preferred embodiment of the presentinvention.

As shown in FIG. 4, the mounting data table includes mountingcoordinates (x, y), mounting angles ψ and the like for each respectivemounting sequence number.

These coordinates (x, y) and mounting angles ψ indicate the values whenthe positional relations are established in an ideal manner as in themaster substrate 4.

Once information on a mounting coordinate (x, y) is provided, the cell R(i, j) where the coordinate (x, y) is located can be identified. Hence,a data section for cell subscripts (i, j) is provided to store theinformation on the subscript (i, j) of the cell where a specificmounting cordinate (x, y) falls on.

Then, as shown in FIG. 5, correction data εx (i, j), εy (i, j) and εθ(i, j) for each respective cell S (i, j) can be obtained from theequations as described in the above and are stored in the correctiondata table 10 according to a two dimensional arrangement of subscripts iand j.

Next, with reference to FIG. 6, an explanation will be made on how eachrespective value of the mounting data table 9 and correction data table10 is utilized after these tables 9 and 10 have been completed.

First, when a mounting sequence number SN is provided to the mountingdata table 9 from the controller 6, the mounting data (x, y, ψ)corresponding to the mounting sequence number SN are read from themounting data table 9.

Also, since the information on the subscripts (i, j) corresponding tothe mounting sequence number SN calls for a cell S (i, j) in thecorrection data table 10, (which means a mounting operation takes placein the cell S (i, j)) the correction values (εx, εy, εθ) at thedesignated cell S (i, j) are read from the correction data table 10. Themounting data (x, y, ψ) are combined with the correction data (εx, εy,εθ) in the controller 6 to produce corrected mounting data (X, Y, θ)(,where X=x+εx, Y=y+εy and θ=ψ+εθ)), which are inputted to the driver 8.

Next, a flow of operational steps of an electronic components mountingmachine in the present exemplary embodiment will be explained withreference to FIG. 7.

First, according to dividing numbers m and n, a master substrate 4 isdivided into cells and information on subscripts (i, j) that correspondto each respective cell is stored in each respective section of amounting data table 9. (Step 1) Then, a substrate 11 (where electroniccomponents are actually mounted) is set up under a camera 5. (Step 2)

A measurement of each respective coordinate of recognition marks A', B',C' and D' is performed by the camera 5. (Step 3)

The substrate 11 is also divided into cells of S (i, j) and informationon correction values εx(i, j), εy(i, j) and εθ(i, j) applicable to eachrespective cell of S (i, j) is stored in a correction data table 10.(Step 4)

Next, the mounting sequence number SN is reset to 1 by a controller 6(Step 5) and it is confirmed that the mounting sequence number SN hasnot reached the last mounting sequence number END. (Step 6)

Then, as described in FIG. 6, follow the procedures of reading theinformation on mounting data x, y and / , and also correction values εx,εy and εθ, (Steps 7 and 8), obtaining corrected mounting data X, Y and θby calculation, (Step 9), and mounting electronic components accordingto the corrected mounting data X, Y and θ. (Step 10)

More specifically, corrections take place for each respective cell thathas been formed by dividing the substrate 11 into small sections,thereby resulting usually in a different correction value for eachrespective cell.

Therefore, a precise mounting operation can be realized by applying veryfine calibrations to the mounting coordinates and the like.

The procedures of Step 7 to Step 11 are repeated by having the mountingsequence number SN increased by one (Step 11) until the mountingsequence number SN reaches the last mounting sequence number END. (Step6)

When the mounting operation of electronic components on the substrate 11is finished, the substrate 11 is taken out, (Step 12), and the mountingoperation of electronic components on another substrate of the same kindis resumed. (Step 13)

It is needless to say that the method of mounting electronic componentson a substrate employing the same correction method as described in theabove can be used even when recognition marks are located at more thanfour places, the pattern formed by connecting the positions occupied byrecognition marks is not a rectangle, and the positions occupied byrecognition marks coincide with the corners of a regular polygon or apattern formed by combining regular polygons.

The coordinate system, whereby corrections in mounting positions areperformed, can also adopt a coordinate system wherein the X and Ycoordinate axes cross each other making a slanting angle instead of aright angle.

Also, an inclination against a specific coordinate axis can be used inplace of an angle for defining the corrections in mounting positions.

POSSIBLE APPLICATIONS OF THE INVENTION IN THE INDUSTRY

An electronic components mounting machine of the present inventioncomprises an actuator whereby electronic components are mounted on asubstrate, a detector whereby recognition marks located on the substrateat four positions at least are detected and the coordinates of theserecognition marks are measured, a controller whereby the actuator iscontrolled, a mounting data table wherein information on mountingcoordinates and angles for mounting electronic components is stored anda correction data table wherein information on correction values inmounting coordinates and angles for the substrate to be mounted withelectronic components is stored, and has Provision for the correctiondata table to store information on correction values individually for aplurality of cells that are formed by dividing the substrate into smallsections according to a specified rule with a basis placed on thecoordinates of the recognition marks detected by the detector and alsofor the information on the mounting coordinates and angles stored in themounting data table to get adjusted by the correction valuesspecifically stored in the correction data table for each respectivecell to be mounted with a specific electronic component, thus allowingthe electronic components mounting operation to be performed in a finelyadjusted manner by accommodating the factor of deformations of thesubstrate and realizing precise mounting of electronic components on asubstrate even when the substrate is nonuniformly deformed.

What is claimed is:
 1. A mounting method of electronic componentscomprising the steps of:obtaining a correction value for each of aplurality of cells, said plurality of cells formed by dividing asubstrate into a plurality of small sections according to a predefinedrule, said correction values based on at least four recognition marksthat are provided on said substrate; and mounting electronic componentson said substrate by applying said correction values to mountingcoordinates and mounting angles corresponding to electronic componentsmounted on an ideally formed substrate.
 2. The mounting method ofelectronic components according to claim 1, wherein actual measurementsmade on a master substrate that has no deformation are used as standardvalues, on which said correction values are based.
 3. The mountingmethod of electronic components according to claim 1, wherein designvalues are used as standard values, on which said correction values arebased.
 4. The mounting method of electronic components according toclaim 1, wherein corrected mounting coordinates are expressed accordingto a rectangular-coordinate system.
 5. The mounting method of electroniccomponents according to claim 1, wherein corrected mounting angles areexpressed by angles which form with a specified reference line.
 6. Themounting method of electronic components according to claim 1, whereinsaid each of said plurality of cells formed by dividing said substrateinto a plurality of small sections according to a specified rule is arectangle.
 7. A method of mounting components on a substrate, saidmethod comprising the steps of:partitioning a master substrate so as todefine a plurality of cells, said master substrate having at least fourrecognition marks formed thereon, said master substrate being free fromdefects, partitioning a second substrate so as to define the sameplurality of cells as said master substrate, said second substratehaving the same recognition marks as said master substrate, generatingand storing a mounting data table, said mounting data table containinginformation on mounting coordinates and mounting angles of componentsmounted on said master substrate, detecting location coordinates foreach of said at least four recognition marks formed on said secondsubstrate, generating correction values for each of said plurality ofcells of said second substrate, said correction values generated fromthe location coordinates of said recognition marks, storing saidcorrection values for each of said plurality of cells in a correctiondata table, calculating corrected mounting data for each of saidplurality of cells of said second substrate in which a component is tobe mounted, said corrected mounting data calculated utilizing saidcorrection values, mounting said components on said second substrate,each component designated to be mounted in a given cell of saidplurality of cells being mounted in accordance with the correctedmounting data corresponding to said given cell.
 8. An electroniccomponents mounting machine comprising:an actuator for mountingelectronic components on a substrate; a detector for detectingcoordinates of recognition marks formed on said substrate, at least fourrecognition marks formed on said substrate; a controller coupled to saidactuator and said detector, said controller operable for controllingsaid actuator and said detector; means for storing a mounting datatable, said mounting data table containing information on mountingcoordinates and mounting angles of electronic components to be mountedon said substrate; and means for storing a correction data table, saidcorrection data table containing information on correction values to beapplied to said mounting coordinates and mounting angles, saidcorrection data table storing information on correction values for eachof a plurality of cells, said plurality of cells formed by dividing saidsubstrate into a plurality of small sections according to a predefinedrule, each of said small sections corresponding to a given cell, saidcorrection values based on said coordinates of said recognition marksdetected by said detector, said controller enabling said actuator tomount said each respective electronic component in accordance with theinformation on said mounting coordinates and mounting angles stored insaid mounting data table after the information is corrected according tosaid information on correction values stored in said correction datatable for each respective cell in which a corresponding electroniccomponent is mounted.
 9. The electronic components mounting machineaccording to claim 1, wherein actual measurements made on a mastersubstrate that has no deformation are used as standard values, on whichsaid correction values are based.
 10. The electronic components mountingmachine according to claim 1, wherein design values are used as standardvalues, on which said correction values are based.
 11. The electroniccomponents mounting machine according to claim 1, wherein the detectorfor detecting recognition marks is a video camera.
 12. The electroniccomponents mounting machine according to claim 1, wherein correctedmounting coordinates are expressed according to a rectangular-coordinatesystem.
 13. The electronic components mounting machine according toclaim 1, wherein corrected mounting angles are expressed by angles whichform with a specified reference line.
 14. The electronic componentsmounting machine according to claim 1, wherein said each of saidplurality of cells formed by dividing said substrate into a plurality ofsmall sections according to a specified rule is a rectangle.